A variety of disease conditions, including the response to treatment of a disease state, can be monitored by hematology markers, using the approximate concentration of certain white blood cells in a blood sample as an indicator of the body's response to the disease. For example, the concentration of CD4+ T-lymphocyte cells in a blood sample may provide a marker for the outbreak of AIDS following HIV infection. A cell count of lower than about 200 cells/μl blood indicating a seriously weakened immune system and thus the need to immediately start with e.g. antiretroviral treatment (ART). Some disease conditions, such as viral or bacterial infection, are characterized by an increased concentration of blood leukocytes, e.g., above about 10,000 cells/μl blood, which can thus serve as an indicator of an infectious disease state. Conversely, the concentration of leukocytes in a blood sample may be depressed, e.g., below about 4,000 cells/μl blood, in an individual who has leukemia or who is undergoing chemotherapy or radiation therapy. In these and other disease conditions which are characterized by depressed or elevated levels of a white blood cell type, the level of the marker cells can be used to detect or confirm a disease condition, or monitor the body's response to treatment of the condition.
Currently, there are two general hematological methods that are commonly employed for determining the concentration of given cell in a cell sample. In a first approach, the cell type of interest is labeled with a marker that binds specifically to that cell type, typically an antigen-specific antibody. The cell sample is then analyzed with a cell counter, e.g., a flow cytometer or a Fluorescence Activated Cell Sorter (FACS) to determine the percentage of to cells having the surface-bound marker.
The second general approach is to label cells of interest and examine a representative cell volume by microscopic examination, counting the number of labeled and unlabelled cells to determine a percentage of the cell type of interest.
In both approaches, particularly where it is desired to determine the concentration of a given white cell type, the cell sample may first be treated to remove red blood cells or other unwanted cells.
The methods outlined above are well suited to laboratory or clinic settings where there well-trained laboratory personnel and cell-sorting or histology equipment is available. However, they do not lend themselves readily to field settings, such as storefront clinics, or field clinics in third-world countries, where neither trained laboratory personnel or sophisticated cell sorting or microscope equipment are present. In poorer areas of Africa, for example, these methods may be ill suited for testing large numbers of people for CD4+ T cell counts, as an indication of the onset of AIDS following HIV infection, or for monitoring a person's response to e.g. antiretroviral drugs.
It would thus be desirable to provide simple, rapid, inexpensive kit and method for determining cell counts on disease-related cells, e.g., selected white cells in a blood sample. In particular, such a method and kit should be easily executable with only minimal training, and require little or no special lab equipment, e.g., beyond a simple, e.g. manually driven table-top centrifuge.